供电器原理及故障检修实例

1供电器工作原理 供电器也称电源供给器、电源插入器，或者叫集中供电器，其作用是将220V交流市电变为放大器或光接收机所需的低压60V交流电，供放大器或光接收机作为电源。供电器一般具有过载保护功能，一旦供电回路过载或出现短路故障，供电器自动切断60V输出电源，避免损坏供电器的电源变压器。     

磁饱和稳压型供电器维修心得

在有线电视线路中，大部分采用磁饱和稳压型供电器，此供电器能在交流电压140～260V之间正常工作，适合在农村有线电视线路中使用，但也有不足之处，就是使用1年以上的供电器容易出现输出电压下降，这是由磁饱和稳压型供电器里的电容引起。     

谈电缆电视干线供电系统设计

本文针对电缆电视网络的实际情况，根据放大器恒压电源的伏安特性及从电系统最低同荷要求，对供电系统的容量，供电器数量，供电器位置等参数进行了分析计算。     

浅谈有线电视集中供电的计算方法

介绍有线电视集中供电的计算方法，决定供电器所能带的放大器级数的是放大器功率的大小和放大器级间电缆回路电阻的大小，集中供电器供电连接方式不同，相同输出功率的集中供电器所带的放大器级数也不相同。施工时采用正确的供电连接方法，才能确保选用的供电器发挥较高的效率。     

改进优尼卡PS—6A电源供应器

美国优尼卡（ＵＮＩＫＡ）公司生产的有线电视ＰＳ－６Ａ电源供电器在国内中型有线电视系统中使用较为广泛，但所有用户都有这样体会：当在调试干线系统时放大器一旦瞬间短路该电源供电器就开始报警，很长时间消除不了，也无法知道干线是否还在短路，这样就影响线路检修时间，为此很多用户改用其他 ＡＣ ６０ Ｖ供电器取而代之。我台早期针对该供电器进行剖析，并进行改进，目前使用较为安全方便，再也不会出现长时间报警。现改进后有复位按钮，可以及时消除报警，最大特点是设置了短路指示灯（原来标明短路指示灯实际上是故障报警灯）。 Ｕ…     

有线电视线路供电分析

介绍采用倒推法计算供电器的馈电级数以及通过降低回路电阻提高供电级数的方法；描述影响供电器馈电级数的主要因素，以及如何估算供电器实际功耗，及时发现传输过程中的偷漏现象。     

3例故障检修

（1）某小区有几幢楼收不到有线电视信号。这几幢楼的“楼放”为60V供电，印V供电器的电源指示灯不亮。供电器和该幢楼的220V放大器共用一个电源插座，拔下这两个插头，发现供电器电源插头的金属片被烧了一个缺口，且与该插头连接的插孔处被烧焦而变形，但接220V放大器的插头和插座均完好无损。用万用表测有223V电压，此时再将供电器的插头插入，223V电压不见了，原来这223V电压是虚电，只要一加上负载，电压即为O。检查供电器电源线与电力三相四线接头处，剥开绝缘胶布发现电源线的铝芯被氧化成粉末状，一碰便脱落下来。原来小灵通基站的电源也取自该处，而他们的电源线是铜丝的，和我们的铝芯线缠绕在一起接在电力铝芯线上，并用绝缘胶布包起来。在潮湿、高温的环境下，铝和铜发生化学反应，致铝芯被氧化成粉末状，而印V供电器比220V放大器产生的电流大，在接头处打火产生的热量高，导致该插头和插座均被烧坏。在电力线上重新开口接好电源线，并用胶布包好，再抉掉插座，故障排除。     

馈电线路短路维修1例

某片区信号突然中断，该片区信号从电业小区出来由两台60V放大器串接所带，检查供电电源及信号源，发现供电器输出保险丝烧断，更换新的保险丝又被烧断。测试供电器输入电压为220V，输出电压为60V，分析供电器及其所带线路有短路。沿线路逐级查找未发现异常情况，把该线路的第二级60V放大器断掉检查第一级放大器，发现供电器工作正常．第一级放大器工作正常，而第二级放大器不再向下馈电，这说明问题出在两级放大器之间或第二级60V放大器上。为了排除后一种情况，更换第二级60V放大器，重新接通线路，并用供电器供电．这时供电器仍然烧保险丝，这说明问题不在第二级60V放大器．而在两级放大器之间。     

有线电视供电器的改进

有线电视供电器的改进□李建贵（西安中航工程公司７１００００）在有线电视工程中，通常采用交流供电器为干线放大器提供６０Ｖ交流电源。如果使用进口带开关电源的干线放大器，如加拿大三皇冠ＬＡ系列和ＴＢ系列，启动电流大，采用输出功率较小的供电器，一供电过压保护...     

供电器原理及故障检修实例

1 供电器工作原理 　　供电器也称电源供给器、电源插入器,或者叫集中供电器,其作用是将220 V交流市电变为放大器或光接收机所需的低压60 V交流电,供放大器或光接收机作为电源.供电器一般具有过载保护功能,一旦供电回路过载或出现短路故障,供电器自动切断60 V输出电源,避免损坏供电器的电源变压器.……     

Noise figure for erbium-doped optical fibre amplifiers

A rate equation model is used to calculate the excess noise figure for erbium-doped fibre amplifiers. It is shown that erbium amplifiers can operate with high gain and can have noise figures only 0.2 dB above the quantum limit     

含运算放大器的一阶电路时间常数的计算

时间常数是一阶动态电路分析中的一个重要参数。而含运算放大器的一阶电路时间常数的计算又是学习中的难点。本文采用了经典法、外加电源计算和电路等效三种求解手段讨论含运算放大器的一阶电路时间常数的计算。并针对含运算放大器的一阶电路的三种基本情况,详细介绍了零电流支路开路和等电位点之间短路这两种电路等效手段的应用,展示了电路等效变换在求解此类问题时的便捷之处。     

Theoretical power output and bandwidth of traveling-wave amplifiers

Expressions are developed to calculate the theoretical power output of traveling-wave amplifiers using any type of RF structure. Calculations are made for helix-type tubes and it is shown how to calculate the power output of tubes using more dispersive structures in terms of calculations made for helix tubes. The principal factors accounting for higher power output of dispersive structures are presented and discussed. The gain and bandwidth of forward-wave helix amplifiers are derived from the small-signal theory as functions of frequency and it is shown that the gain in db times the frequency bandwidth is a constant as a function of helix length for highgamma_{0}a'and the gain times the bandwidth squared is a constant for lowgamma_{0}a'.     

Effects of multiple wave mixing and gain saturation in an idealtraveling wave semiconductor laser amplifier

Nonlinear distortions induced by four-wave mixing and gain saturation in a semiconductor laser amplifier can affect the overall performance of lightwave systems using such devices. A model which includes both types of distortion in a three-channel optical transmission system is presented. Large-signal analysis is used to calculate distortion in amplifiers operating near saturation. The technique provides more realistic predictions than the small-signal rate equation analysis used in previous theoretical studies of four-wave mixing in optical amplifiers     

Reductionl of Interference Due to Common Mode Voltage in Biopotential Amplifiers

We review how the nonideal properties of biopotential amplifiers can transform common mode voltage into interference. We then review several design approaches for two-and three-electrode amplifiers, both nonisolated and isolated, that reduce this interference. We consider the effects of static electricity on the various designs, and we show how to calculate the optimal values of the circuit components.     

On the harmonic distortion coefficients of active-loaded amplifiers

Starting from the modified Ebers-Moll model which represents the Early effect more accurately than conventional models with the Early voltage, new expressions to calculate the harmonic distortion coefficients of active-loaded BJT amplifiers are derived and applied to the determination of the optimum operating point, where the total harmonic distortion is at a minimum. The results are not obtainable with SPICE, therefore derived expressions provide the possibility of completing the simulation with manual calculations.     

Design of waveguide structures for polarization-insensitive opticalamplification

By analyzing several types of waveguide structures, we demonstrate that a polarization-insensitive semiconductor optical amplifier can be designed by using an anisotropic gain medium or a properly shaped active region. In particular, we calculate the waveguide parameters required for achieving polarization-insensitive optical amplification and discuss their tolerances. Our results show that considerable flexibility in the design of polarization-insensitive amplifiers can be offered by tailoring the waveguide structures of the amplifiers     

Multichannel amplification in strongly pumped EDFAs

Multichannel erbium-doped fiber amplifiers (EDFAs) are analyzed based on a rate-equation model. Forward pumping is considered and amplified spontaneous emission (ASE) as well as scattering loss are taken into account. An analytical approximation to calculate the amplification in high-power multichannel EDFAs is also introduced in this paper. Results for both the numerical and approximate analytical models are derived and discussed. It is shown that under the considered conditions, the analytical solutions provide a good approximation to the exact numerical solution and thus may be used for the design of such amplifiers.     

长周期光纤光栅(LPG)均衡滤波器在光纤放大器中的应用

根据耦合模理论 ,给出了两级关联和非关联长周期光纤光栅的透射率表达式 ,从而指出在进行LPG均衡滤波器设计时 ,应采用非关联的光栅 ,可以构成灵活多变的透射谱 ,非常适合光纤放大器的不同增益谱对均衡滤波器传输特性 (透射谱 )的不同要求。以此为基础 ,设计和模拟计算了 LPG均衡光纤宽带放大器的增益及噪声谱。结果表明 ,采用均衡滤波方式是使光纤放大器增益平坦的有效方法     

Noise evolution along optically amplified links in presence ofnonlinear parametric gain

With a semiclassical model of the optical amplifier, we calculate the evolution of noise along optically amplified lines in presence of nonlinear interaction between signal and amplified spontaneous emission, amplifier saturation, fiber dispersion and vacuum field fluctuations associated with attenuation of the fiber. The noise figure (NF) is calculated for two representative cases of long and short-distance links with different numbers of optical amplifiers and for several fiber dispersions. Results indicate that the optimum number of optical amplifiers is limited by the increase of nonlinear effects with signal power